I'd like to be able to pay with my phone. My iPhone.
I know Apple does not allow this, but there is no such app in Cydia, either
I've made one. It supports TradeHill, ExchB, CampBX, InstaWallet and Mt. Gox (once Gox finally get back to me about their API activation, I can finish and release it). Depending on the service, you can trade, withdraw/deposit, and the all-important pay/receive with QR-codes. The first version just supports TH and is a simple trading app, but it is available on Cydia and the source is at
https://github.com/teeman/BitcoinTrader. If you, or anyone else, has a jailbroken iPhone and want to give me some feedback on the new version, shoot me a PM.